The objective of this proposal is to isolate and characterize the different apolipoprotein and lipoprotein forms of lipoprotein D (LP-D) and to clarify the relationship between LP-D and lecithin:cholesterol acyltransferase (LCAT). It is hypothesized that LP-D is the substrate-product carrier of LCAT action and LP-D is involved in the redistribution of cholesterol/cholesterol esters between various lipoprotein species and/or peripheral membranes. The specific aims of the proposed research are to 1) isolate and characterize the multiple forms of ApoD, 2) isolate and characterize the multiple forms of LP-D, 3) isolate and prepare antiserum to purified LCAT, and 4) examine the structural and metabolic relationship between LP-D and LCAT.